As a related art of the present invention, there is a constitution that a displacement control valve is attached to a variable displacement compressor (for example, refer to Patent Document 1 described in a following column 0011). A constitution which is similar with the variable displacement compressor is shown in FIG. 6. FIG. 6 is whole cross sectional views showing a displacement control valve connected with a variable displacement compressor. A displacement control valve 100 is equipped within a mounting portion which is not shown in the displacement control type compressor 100. However, in order to clarify the displacement control valve 100, the valve is shown as taken out from the variable displacement compressor 150.
The variable displacement compressor 150 of FIG. 6 will be specified briefly. In FIG. 6, the variable displacement compressor 150 is formed by a casing to form an outer shape composed of a cylinder block 151 to which a plurality of cylinder bore 151A is provided, a front housing 152 provided at an end of the cylinder block 151, a rear housing 153 connected to the cylinder block 151 via a valve plate device. A crank chamber (control chamber) 155 defined by the cylinder block 151 and the front housing 152 is provided to the casing. A transverse shaft 156 is provided in the crank chamber. A skewed plate having a disc shape is arranged at a peripheral of a center portion of the shaft 156. The skewed plate is composed so as to have an angle incline the skewed plate 157 to the shaft 156 by connecting a long hole of a connecting portion 159 and a pin of a rotor 158 fixed to the shaft 156. Note that a side face of the rotor 158 is supported by a bearing 176.
One end of the shaft extends to an outer portion with penetrating in a boss portion 152A which projects to an outside of the front housing 152. A seal portion 152B is provided at an inner circumference of the boss portion 152A. The crank chamber 155 is sealed internally by the seal portion 152B.
A bearing 175 is arranged between the shaft 156 and the boss portion 152A. Further, a bearing 177 is provided at another end of the shaft 156. And the bearings 175, 177 support the shaft 156 rotatably.
Respective pistons 162 are provided in a plurality of cylinder bores 151A provided on a circumference in the cylinder block 151. Further, a recess portion 162A is provided at an inner side of one end of the piston 162. Then, outer circumference of the skewed plate 157 is connected slidably via a shoe 163 arranged in the recess portion 162A of the piston 162. Also, it is constituted that the skewed plate 157 and a connecting portion 159 are rotatably connected each other via a link mechanism.
In the rear housing 153, a discharge chamber 164 and an air inlet chamber 165 are formed and partitioned. The air inlet chamber 165 and an inside of the cylinder bore 151A communicate with via a suction valve provided on a valve plate device 154. Also, the discharge chamber 164 and the inside of the cylinder bore 151A communicated with via a discharge valve provided on the valve plate device 154.
Next, with respect to a displacement control valve 100 equipped to the variable displacement compressor 150 will be specified briefly. The displacement control valve 100 is composed on a solenoid portion 140 and a valve portion 115. A suction chamber 165 of the variable displacement compressor 150 communicates with a suction valve chamber 126 via a suction fluid passage 110 for an inlet pressure Ps. Also, the discharge chamber 164 communicates with a discharge valve chamber 106 via a discharge fluid passage for a discharge pressure PD. Further, the crank chamber 155 communicates with a control valve chamber 104 via a control fluid passage 109 for a control pressure Pc. Then, a valve portion 121 acts by a cooperating action by a movable iron core 142 integrally with a rod 120 which operates in response to an amount of current flows in a electromagnetic coil 145 of the solenoid portion 140, and a force acts on a pressure sensing device 122 provided in the control chamber 104 of the valve unit 115. The valve unit 115 controls a fluid of the control pressure Pc by open and close between a control valve chamber 104 and a discharge valve chamber 106 according to an action of the valve portion 121. In a constitution of the existing displacement control valve 100, the control valve chamber 104 does not communicate with the suction valve chamber 126 even as the valve portion 121 opens and closes the valve.
In the variable displacement compressor (clutch less compressor) 150 to which the displacement control valve 100 is provided, the skewed plate 157 co-rotates by rotation of the rotor 158. Also, an angle of inclination of the skewed plate 157 changes in response to the control pressure PC in the crank chamber 155. Further, the piston 162 moves as reciprocate motion, in response to the change of the angle of inclination of the skewed plate 157. A refrigerant discharged from the discharge chamber 164 according to the reciprocating motion of the piston 162 is provided to an evaporation chamber G from an expansion valve via a condensing chamber P. In this process, the variable displacement compressor 150 returns the refrigerant to the suction chamber 165 with cooling the vehicle interior. Note that, the control pressure Pc of the crank chamber 155 is determined by a flow amount flew from the discharge chamber 164 to the crank chamber 15 in response to a valve opening degree of the displacement control valve and a discharge amount discharged through a fixed orifice 170 provided on the variable displacement compressor 150. There are times when liquid refrigerant exists in the crankcase and it is desirable to increase the cross-sectional area of the fixed orifice 170 so that the liquid refrigerant vaporizes rapidly. However, normal pressure control in the crank chamber 155 becomes problematic and this cross-sectional area cannot be enlarged.
Then, in a region where there are warm and cold on day and night, after the variable displacement compressor 150 stops, then, when it becomes night and temperature decreases, the refrigerant gas is liquefied and pools in the crank chamber 155 of the variable displacement compressor 150. This variable displacement compressor 150 can only be operated at minimum capacity when it is started until crank chamber pressure decreases to a pressure close to suction chamber pressure, which takes a relatively long time since the crank chamber 155 communicates with the suction chamber 165 only via the fixed orifice 170. The crank chamber pressure is greater than the suction chamber pressure because the liquid in the crank chamber 155 is evaporating faster than the vapor can exit to the suction chamber 165 through the fixed orifice 170. The crank chamber pressure does not decrease until all the liquid refrigerant is evaporated and discharged. Thus, without increasing the refrigerant flow rate out of the crank chamber 155, the compressor does not operate at a normal capacity for an extended time up to 5 minutes and passenger comfort is poor for several minutes more. There is a problem. The orifice needs to be small to be able to control crank chamber pressure and it also needs to be large to permit the compressor to start and operate at normal capacity after less than a minute. Then, upon solving this problem, in order to minimize the product cost of the variable displacement compressor 150, it is required to improve a function of the displacement control valve 100 from the market.
[Patent Document 1] Japanese Patent Laid Open No. 2003-322086 (FIG. 6 and the like)